The main goal of this project is the elucidation of host defense mechanisms involved in recovery from virus-induced leukemia in mice. We have approached this problem by attempting to separate various components of the host response against leukemia by identifying individual genes which influence different aspects of this response. Three new genes (Rfv-1, Rfv-2, Rfv-3), which influence recovery from established Friend virus leukemia in mice, have been identified. We now have iformation concerning some of the immune mechanisms influenced by these genes and the interactions that occur among these mechanisms.